Golf ball with hard thin cover

Abstract

A golf ball having a coating layer which is excellent in resistance to impact, scuffing and abrasion without increasing the thickness of the layer. The coating layer has a hardness of 21 to 60 N/mm 2 , which is calculated by the following expression (1): Hardness=(test load)/{26.43×(penetration depth (mm)) 2 }  (1) wherein the test load is 3 mN.

What is claimed is:  
     
       1. A golf ball comprising: 
       a main body; and  
       a coating layer enclosing the main body, wherein the coating layer is formed from a polyurethane comprising a polyisocyanate and a triol and diol in an equivalent ratio of triol to diol of 1.0 to 2.5, said coating layer having a thickness of 5 to 20 μm and a hardness of 21 to 60 N/mm 2 , the hardness being calculated according to the following expression (1),  
       
         
           Hardness=3 mN/{26.43×(penetration depth (mm)) 2 }  (1)  
         
       
       wherein the penetration is effected in a land area of said coating layer by a diamond pyramid indenter loaded with a 3 mN test load. 
     
     
       2. A golf ball according to  claim 1 , wherein the hardness of the coating layer is 35 to 45 N/mm 2 . 
     
     
       3. A golf ball according to  claim 1 , wherein an equivalent ratio of isocyanate group in the polyisocyanate to hydroxyl group in the polyol (NCO/OH) is 0.9 to 1.5.